摘要:

Direct separation of racemic tetrahedral transition metal carbonyl cluster SFeCoMo(CO)8(C2H5OCOCp) has been conducted by liquid chromatography using tribenzoylcellulose as chiral stationary phase. The effects of concentration of 2-propanol, various primary alcohols in the mobile phase and column temperature on the rentention and enantioselectivity of SFeCoMo(CO)8(C2H5OCOCp) cluster enantiomers were studied. The maximum resolution factor obtained was 2.306 when hexane/2-propanol(99.5/0.5,v/v) was used as solvent at 23°C.

ISSN:0003-2719    

DOI:10.1080/00032719708001821

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

A convenient way of resolving the enantiomers of amino acid esters after their derivatization using benzophenone imine is described. The enantiomers of benzophenone Schiff base derivatives of various amino acid ethyl esters are readily separated on three commercially available chiral stationary phases (CSPs). Among them, CSPs 2 and 3 afford generally the base-line enantioresolution for the analytes studied. From understanding of chromatographic results, a plausible chiral recognition mechanism is discussed.

ISSN:0003-2719    

DOI:10.1080/00032719708001822

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

A simple method for atomic absorption spectrometric determination of lead, copper, cadmium and nickel in drinking water samples after preconcentration by sorbing 1-(2-pyridylazo) 2-naphthol (PAN) complex of these metals on an activated carbon column has been established. The metal/PAN complexes were quantitatively retained on the activated carbon in the pH range 6-8. Metals retained on the activated carbon column were completely eluted with 2M HCl in acetone. This method was applied to the determination of lead, copper, cadmium and nickel in drinking water samples and good results were obtained (Recoveries >95%, relative standard deviations <7%, relative error <3%).

ISSN:0003-2719    

DOI:10.1080/00032719708001823

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Simple and rapid chemiluminescence (CL) assays for H2O2, •OH, •O2−and1O2using 5-amino-2,3-dihydro-1,4-phthalazinedione (luminol) or 2-methyl-6-phenyl-3,7-dihydroimidazo[1,2-α]pyrazin-3-one (CLA) as CL reagents were developed. The means of the intra-assay relative standard deviations of ten replicate measurements of H2O2(25-120 μM), •OH generated from Fe(II) ion (2.5-10 μM) in the presence of 980 μM H2O2, •O2−generated from hypoxanthine (HX) (7-50 μM) in the presence of 9 × 10−3units xanthine oxidase (XO) and1O2generated from NaOCl (3-12 mM) in the presence of 97.6 μM H2O2were found to be 4.0%, 2.8%, 2.4% and 8.7%, respectively. To validate the proposed methods, the scavenging abilities of three standard antioxidative compounds, such as L-ascorbic acid, (±)-α-tocopherol and superoxide dismutase (SOD) were examined for four active oxygen species and compared with those by anelectron spin resonance (ESR) spin-trapping method. In addition, the CL methods were also applied to establish the relationships between the decrease of CL intensity and the structures as well as redox characters of syringic acid, 3-hydroxybenzoic acid, 3,4-dihydroxybenzoic acid. From the obtained results, the scavenging effects to H2O2, •OH, •O2−and1O2of other dihydroxybenzoic acids were also evaluated.

ISSN:0003-2719    

DOI:10.1080/00032719708001824

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Zervamicin is a 16-residue antibiotic peptide produced byEm. salmosynnemata.It belongs to a broad class of α-helical peptides which interact directly with the lipid bilayer. In our strategy to investigate the structure and dynamics of membrane-associated peptides we follow an approach based on site-specific isotope labelling and measurement by means of stable isotope sensitive techniques. We have accurately determined the exact postion of deuterium atoms at Gln-11 of the antibiotic zervamicin-IIB from the FAB collision-induced dissociation FAB-mass spectra of the sodium cationized molecules.

ISSN:0003-2719    

DOI:10.1080/00032719708001825

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

A single-line FIA system with a stream-sample splitting device for chloride determination is presented. The analytical method is based on the Fe3+/Hg(SCN)2/Cl−system and the absorbance of the red Fe(SCN)2+species monitored spectrophotometrically at 480 nm. Using a stream-sample splitting device, the recorded signal is composed of two merged peaks. Three calibration curves were obtained, once injecting the standard solution series, two using the maximum heights of P1and P2peaks and one using the height of T trough. The FIA system showed three linear responses to the concentration of chloride in the ranges 10-100 ppm (P1); 10-500 ppm (P2) and 20-1000 ppm (T), respectively. Also, it was capable of detecting chloride ions in different types of water with a throughput of 15 samples h−1and the RSD for 240 ppm of Cl−(n=10) were 1.67% (P1); 2.38% (P2) and 1.23% (T), respectively. The interference of several ions (commonly found in water) on the FIA outputs was investigated.

ISSN:0003-2719    

DOI:10.1080/00032719708001826

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

ISSN:0003-2719    

DOI:10.1080/00032719708001810

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor